With development of communications technologies, communications systems using different wireless communications technologies such as a Global System for Mobile Communications (GSM) using a Time Division Multiple Access (TDMA) technology, a voice communications system using a Code Division Multiple Access (CDMA) technology, and a data communications system using a Long Term Evolution (LTE) technology emerge in succession. Different communications systems correspond to different working frequency bands. To enable a mobile terminal to support different communications systems, an antenna of the mobile terminal may cover a relatively wide working frequency band so as to meet communication quality requirements on different communications systems.
To expand a working frequency band of an antenna of a mobile terminal, a variable capacitor is generally disposed in the antenna of the mobile terminal, where different capacitance values of the variable capacitor correspond to different working frequency bands of the antenna. The working frequency band of the antenna can be adjusted by adjusting the capacitance value of the variable capacitor so as to expand the working frequency band of the antenna so that the variable capacitor is applicable to different communications systems and ensures communication quality. An existing adjustment method of an antenna having a variable capacitor is generally setting a priority of a communications system of multiple communications systems supported by the antenna to a highest priority, determining a capacitance value corresponding to a working frequency band of the communications system with the highest priority, and adjusting a capacitance value of the variable capacitor in the antenna to the determined capacitance value. For example, adjusting a working frequency band of the antenna according to the working frequency band of the communications system with the highest priority. Using an antenna that uses a simultaneous GSM and LTE (SGLTE) technology as an example, if a priority of a GSM system is set to be the highest, a capacitance value of a variable capacitor is adjusted to a capacitance value corresponding to a working frequency band of the GSM system. For example, when the working frequency band of the GSM system is GSM 850 megahertz (MHz), the capacitance value is adjusted to a capacitance value corresponding to GSM 850 MHz regardless of a working frequency band of an LTE system so that communication quality of the GSM system implementing a voice service is the best, but communication quality of the LTE system implementing a data service is very poor.
It can be seen that the adjustment method can only ensure communication quality of a system with a highest priority but cannot give consideration to communication quality of another system with a low priority that is supported by the antenna. Therefore, the adjustment method cannot be applicable to a scenario in which there is a particular requirement on the communication quality of the system with a low priority.